Global vs local
This concept of “global vs local optimization” is often misunderstood. It seems obvious that splitting a process in pieces and improving them separately must improve the global performance of the process. Sadly, this is not necessarily true. What makes a part of the process excel could be exactly what kills other parts. This “what-improves-me-kills-you” effect happens more often than you might think and its effect is terrible, since the less effective part of a process impacts heavily its performance.
This simple example created by the Lean Management Institute illustrates this idea:
Genuine improvement (which means improving things your customer really cares about) rarely happens without a global approach. Focusing in isolated parts of the process will, in the best case, improve the local efficiency of an area or department but will have little impact in your customer’s satisfaction. In the worst case, everything will work much, much worse and you’ll spend hours (weeks, months…) wondering why.